An outboard motor is the most common motorized method of propelling or propulsion system for small, medium, and large watercraft. The primary components of the outboard motor have not changed much since inventor Ole Evinrude introduced his two-cylinder motor—ELTO stood for Evinrude Light Twin Outboard. For example, an outboard motor is a self-contained unit that includes an engine or powerhead, a midsection containing an exhaust housing, gear box and drive shaft, and a lower unit containing a propeller, an exhaust port, and a skeg, wherein the outboard motor is designed to be affixed to the outside of the transom, which is positioned at the stern of a boat or ship. As well as providing propulsion, outboards provide steering control, as they are designed to pivot about their mountings and thus control the direction of thrust or propulsion of the boat. Outboard motors have advanced from two-stroke to four-stroke motors, from 2-, 3- and 4-cylinder models, added fuel injection, electronic timing and other efforts to increase fuel economy, low end torque, and smoother operation.
Even with advances in engine design, (these advances have been largely borrowed from other forms of motorized transportation), the modern outboard is a contradiction, having been with us for over a century it has in fact changed little, the last major advance (which in fact is now a problem) happened over fifty years ago when Carl Keikhaefer of Mercury Marine invented the through the propeller hub exhaust system that to this day allows virtually all modern outboard motors to dump untreated, un-muffled exhaust into the aquatic environment. One disadvantage of the modern outboard, especially two-stroke motors is their inefficiency in burning the oil and gas mixture causing large amounts of pollution (especially oil in the water). Moreover, all outboard motors whether two-stroke to four-stroke motors exhaust untreated pollution (in the form of gases and petroleum particulate) down their midsection and out the propeller exhaust section directly into the water polluting the water and marine life. Moreover, another disadvantage of the modern outboard, motors exhausting untreated noise pollution down their midsection and out the propeller section polluting the water with noise pollution causing marine life to depart from their habitat or flee from the boat noise or become disoriented. Only recently has the true impact of our presence under the surface of the water begun to be recognized (reference documentary Sonic Seas).
Another disadvantage of this approach is its fixed configuration wherein the powerhead, midsection and propeller are designed as a fixed rigid unit and the fixed rigid unit pivots about its mountings or articulate thereabout to control the direction of thrust or propulsion of the boat or to offer directional control of the craft. A fixed powerhead, midsection, and propeller place all the units weight and torque on the pivot pin and steering apparatus, and thus limit the size of the motor. In other words you must turn the entire outboard motor to turn the boat. Imagine if the entire front end of an automobile needed to move right to left for steering rather than just turning the wheels.
Another disadvantage of the modern outboard and its fixed configuration positioning the transmission gear case and the exhaust manifold beneath the surface of the water, in front of the propeller, this creates tremendous drag and as speeds increase begins to literally block the water from the control surfaces and propeller blades by creating a shock wave sufficient to cause a vacuum pocket to begin to form around the submerged lower unit. As speed increases, this undesirable condition can escalate to the point that the water loses contact completely with the control surfaces and the propeller itself. This condition is referred to as “blowing out” the lower unit, and can cause complete loss of control of the craft at high speed. Also, the fully submerged, slipping type propeller generates a powerful vortex around itself due to the water being ejected radially from its center, creating a tornado of rotating water around the propeller unit. Moreover, water ejected radially does not provide thrust or control and is therefore a complete waste of energy. There is almost always a vacuum pocket in the center of the submerged propellers vortex, as a matter of fact; virtually all outboard motors count on this vortex to dump untreated exhaust into the marine habitat. However, as the speed of the rotation increase, centrifugal force will cause a vacuum cavity in the center to grow, as the rotation of the propeller approaches 2000 RPM the vacuum pocket grows until it reaches the blades of the propeller, at this point cavitation begins to occur. Cavitation is defined as pockets of vacuum reaching the propeller blades. These pockets of vacuum when in contact with the blades are an extremely undesirable situation because the propeller will make little or no thrust under these conditions, control of the craft is compromised, and the propeller blades will quickly deteriorate as the scouring action of the cavitation bubbles build up on the surface of the blades. Add to this, the fact that virtually all outboards have an exhaust manifold in this submerged gear case means that at anything above a few miles per hour, the hydrostatic drag of just pushing this assembly through the water is very, very high. Therefore a completely submerged propeller while effective and even desirable at low speeds becomes a liability at higher speeds.
The vast majority of boats under 50 feet in length are plaining type hulls, these hulls are designed to enable the boat to step up “on top” of the water while the boat is underway, with the hull “on top” of the water, the boat is able to achieve speeds that make cruising to more remote destinations practical. Whether for work or pleasure it is always desirable to get to where you're going as quickly as possible. This is where the shortcomings of current outboard motors become glaringly evident. Modern boats are quite capable of traveling safely at speeds over 50 MPH, however, fuel efficiency degenerates incredibly quickly at speeds over 25 mph. Modern engine technology is such that fuel efficiency in the engine itself has made great strides. However at the mentioned comparatively low speeds the current outboard motor, even with the latest technically advanced engines, dramatically loses efficiency. While some fuel efficiency is always lost as speeds increase due to well documented factors such as drag coefficient, in the case of the outboard motors the tradeoff is so profound as to be unacceptable.
As the water craft begins to move hydrostatic drag is created by the lower unit, exhaust pipe, and transmission (gear box) located below the surface, causes the even the most modern outboard motor to become dramatically inefficient, even at very low speeds. Outboards today overcome the problems intrinsic in their design by simply adding power until they overcome the drag and with that comes fuel consumption, massive fuel consumption. Larger boats searching for the performance and versatility of the outboard motor are required to employ exotic and expensive multiple engine instillations. This solution is costly and inherently inefficient as it must push two or more of the parasitic lower units through the water as well as the weight and complexity of multiple controls and support apparatus. Such outboards have a narrow and tall profile.
Another disadvantage of the modern outboard is its actual performance is limited by poor efficiency in the system that actually converts the power to thrust. Most medium to larger fishing boats cannot exceed 60 miles per hour and get less than three (3) miles to the gallon. Increases in performance come at crippling cost; usually multiple outboard engines, and fuel mileage measured is in fractions of one mile to the gallon. While it is true some smaller four stroke boats operating at 25 MPH or less can reach ten MPG, when these craft, operated are only slightly faster, and the fuel mileage deteriorates precipitously. All but a tiny fraction of standard size fishing boats average single digit fuel economy. Boats of 17 feet or better, boats with duel engines or boats that operate in excess of fifty miles per hour most often dip below one (1) MPG, making the outboard powered boat, the boats that populate the waterways by the millions, one of the most inefficient forms of transportation ever devised.
Another disadvantage of the modern outboard is it has almost exclusively one forward gear with the propeller acting as a torque converter and transmission, imagine your automobile stuck in low gear or having to start off in high, either condition results in very poor performance and fuel inefficiency. Used in this manner the propeller must be a compromise between low speed slip and high speed thrust, and the results are a unit that does neither particularly well, and boats that, when operated at speeds above twenty five 25 MPH, are very inefficient.
The current outboard motor relies on the propeller to “slip” in the water allowing it to have a “fluid coupling” action, a kind of “torque converter” effect has served to allow marine propulsion systems in general and outboard motors in particular to get along with almost no development other than in the propeller itself.
High speed drives, such as Arneson surface drives, are specialized propulsion units for water craft designed to enable the propeller blades to break the water's surface, these are called surface-piercing propellers. Surface drives do not expose the entire gear case to the water as do standard propeller drive systems with their fully submerged propellers. These drives provide profound performance and efficiency gains at higher speeds. However, these systems are primarily limited to larger craft because the great disadvantage to these surface drives is they are expensive and require the engine to be inboard (inside) the craft, therefore these superb units are only utilized with custom or specialized power boats, such as high-performance speed boats, performance yachts, and military or coast guard boats. Moreover, surface drives make low speed maneuverability, such as docking more challenging since the propeller blades lack the blade surface area contacting the water to generate large thrust at low propeller speeds found in a submerged propeller. Therefore these instillations usually require the use of separate low speed thrusters for docking and maneuvering in close quarters such as a harbor.
Therefore, it is readily apparent that there is a need for an outboard motor and methods of use thereof that functions to enable a combination of features including the midsection and/or propeller to pivot about the powerhead, treat motor exhaust and discharge to the atmosphere eliminating water and noise poisonous water pollution discharge into the water and spread over miles, enable the propeller depth to be raised to surface-piercing and lowered to fully submerged propeller during propulsion to improve propulsion efficiency at both high and low speeds respectively, and reduce the lower unit and gear box size to reduce the source of crippling hydrostatic drag, and thus, improve the performance and fuel efficiency of the outboard motor.